What is being switched off?

The Public Switched Telephone Network (PSTN) and Integrated Services Digital Network (ISDN) are being retired as part of Openreach's programme to move all voice and data traffic to IP-based networks.  This affects:

  • Analogue landlines and ISDN2 or ISDN30 circuits
  • ADSL and FTTC broadband delivered over copper lines
  • Alarm and CCTV systems that dial out over a phone line
  • Lift emergency lines and door entry systems
  • Fax machines, franking machines, and dial-up card payment terminals

The whole of the UK is affected, with the exception of the Isle of Man, Guernsey, Jersey, and the KCOM network in Hull.

What happens if you do not migrate?

When your local exchange is migrated to all-IP operation or when the final switch-off occurs in January 2027, your ISDN and analogue lines will simply stop working. No incoming calls, no outgoing calls, no fax transmissions, no alarm monitoring. Your business becomes unreachable by phone overnight.

There is no extension, grace period or workaround.

Your replacement options

Three mainstream replacements are available, all running over an IP connection (typically business fibre or SOGEA):

  • SIP trunking: replaces ISDN lines at a lower monthly cost while letting you keep your existing on-site phone system, provided it is SIP-compatible. You will need a business fibre or SOGEA connection and a SIP-capable PBX or gateway.
  • Hosted cloud phone systems: These provide a fully managed, scalable solution without requiring on-site PBX hardware. You get greater flexibility, remote working capabilities, and reduced maintenance, needing only a fibre or SOGEA connection and handsets or softphones.
  • Microsoft Teams Calling: integrates telephony directly into Microsoft 365 for organisations already using Teams. This requires a Teams Phone licence plus either a Microsoft calling plan or Direct Routing via a certified session border controller.

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Migration timeline and checklist

  • Now: Audit all services using PSTN/ISDN lines, including alarms, lifts, and payment terminals.
  • Q4 2026: Select your replacement (SIP, hosted VoIP, or Teams Calling) and order business fibre or SOGEA if not already in place.
  • Q1 2027: Complete number porting, configure call routing, and test thoroughly before cutover.
  • Before 31 January 2027: Ensure all services are migrated and legacy lines decommissioned.

Why act now?

Openreach stopped selling new PSTN and ISDN products nationwide in September 2023.  Throughout 2026, the bulk migration phase is underway as Openreach works with providers to move remaining customers onto IP-based services.  Waiting risks last-minute price increases, limited availability of migration resources, and potential service gaps during the transition.